umbillicus

‖n. [ L. See Umbilic. ] 1. (Anat.) The depression, or mark, in the median line of the abdomen, which indicates the point where the umbilical cord separated from the fetus; the navel; the belly button, in humans. [ 1913 Webster ]

2. (Gr. & Rom. Antiq.) An ornamented or painted ball or boss fastened at each end of the stick on which manuscripts were rolled. Dr. W. Smith. [ 1913 Webster ]

3. (Bot.) The hilum. [ 1913 Webster ]

4. (Zool.) (a) A depression or opening in the center of the base of many spiral shells. (b) Either one of the two apertures in the calamus of a feather. [ 1913 Webster ]

5. (Geom.) (a) One of the foci of an ellipse, or other curve. [ Obs. ] (b) A point of a surface at which the curvatures of the normal sections are all equal to each other. A sphere may be osculatory to the surface in every direction at an umbilicus. Called also umbilic. [ 1913 Webster ]